Hello @ksapia
When my Charge 5 battery started to rapidly lose power, I restarted and recharged my device multiple times over several days. This process eventually got my device "unstuck" and the battery went back to lasting 6-7 days. There's no guarantee that this will work for you, but it might be worth a try.
You might also want to check to see if you have features turned on that drain the battery more quickly. This help page has tips you might want to consider: Can I extend my Fitbit device's battery life
Rieko | N California USA MBG PE